The effect of gamma-irradiation on soluble collagen.
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ABSTRACT:
SUBMITTER: Davidson RJ
PROVIDER: S-EPMC1198606 | biostudies-other | 1968 Mar
REPOSITORIES: biostudies-other
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Project description:1. The effect of gamma-irradiation in the range 1 krad-10 Mrads on freeze-dried acid-soluble collagen was studied. 2. The specific-rotation and reduced-viscosity recoveries after heating and cooling of the irradiated collagen in solution showed a high degree of dependence on irradiation dose, with reduced viscosity showing significantly less recovery than specific rotation on increasing the irradiation dose. 3. The dependence of reduced viscosity on concentration was greatly decreased with increased doses of gamma-irradiation. 4. The melting temperature measured by optical rotation also decreased as the irradiation dose was increased, and at low doses was distinctly biphasic. 5. Physical properties showed that the action of gamma-irradiation up to 10 Mrads occurred in two distinct phases, with the early changes being extremely sensitive to irradiation dose. 6. The action of the gamma-irradiation is discussed in terms of the structure of tropocollagen.
| S-EPMC1184632 | biostudies-other
Project description:1. The effect of ultraviolet irradiation on acid-soluble and neutral-salt-soluble calf-skin collagen was studied by chromatography, gel filtration, amino acid analysis and sedimentation of the sub-units, and the reaction kinetics of degradation were obtained from viscosity and optical rotation measurements. 2. It was demonstrated that, whereas the structure of neutral-salt-soluble calf-skin collagen may be represented by the formula (alpha(1))(2)alpha(2), the acid-soluble extract has the formula alpha(1).(alpha(2))(2). The acid-soluble collagen is also unusual in containing a large amount of a component that could be beta(22). 3. Ultraviolet irradiation causes the progressive degradation of the collagen molecule into smaller molecular fragments that subsequently lose their helical nature. The rate constants show that the denaturation of soluble collagens by ultraviolet irradiation is much slower, under the conditions used, than denaturation by heat or enzymes.
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Project description:1. A study has been made of the effect of ultraviolet irradiation on the conformational changes taking place in cooled solutions of thermally denatured acid-soluble calf-skin collagen. 2. The increase in negative rotation and viscosity at 15 degrees for irradiated and thermally denatured collagen solutions becomes less as the irradiation dose is increased. 3. The principal effect of ultraviolet irradiation is the fission of the primary collagen chains, eventually yielding chain lengths incapable of stabilizing a helical structure. 4. The effects of ultraviolet irradiation on acid-soluble collagen may be closely correlated with similar effects on neutral salt-soluble collagen.
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Project description:UNLABELLED: BACKGROUND: Deinococcus deserti VCD115 has been isolated from Sahara surface sand. This radiotolerant bacterium represents an experimental model of choice to understand adaptation to harsh conditions encountered in hot arid deserts. We analysed the soluble proteome dynamics in this environmentally relevant model after exposure to 3 kGy gamma radiation, a non-lethal dose that generates massive DNA damages. For this, cells were harvested at different time lapses after irradiation and their soluble proteome contents have been analysed by 2-DE and mass spectrometry. RESULTS: In the first stage of the time course we observed accumulation of DNA damage response protein DdrB (that shows the highest fold change ~11), SSB, and two different RecA proteins (RecAP and RecAC). Induction of DNA repair protein PprA, DNA damage response protein DdrD and the two gyrase subunits (GyrA and GyrB) was also detected. A response regulator of the SarP family, a type II site-specific deoxyribonuclease and a putative N-acetyltransferase are three new proteins found to be induced. In a more delayed stage, we observed accumulation of several proteins related to central metabolism and protein turn-over, as well as helicase UvrD and novel forms of both gyrase subunits differing in terms of isoelectric point and molecular weight. CONCLUSIONS: Post-translational modifications of GyrA (N-terminal methionine removal and acetylation) have been evidenced and their significance discussed. We found that the Deide_02842 restriction enzyme, which is specifically found in D. deserti, is a new potential member of the radiation/desiccation response regulon, highlighting the specificities of D. deserti compared to the D. radiodurans model.
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Project description:1. A study has been made of the effect of ultraviolet irradiation, in the presence of air and nitrogen, on the conformational changes taking place in cooled solutions of gelatin prepared from thermally denatured neutral-salt-soluble collagen. 2. The increase in negative rotation and viscosity at 15 degrees for irradiated and thermally denatured solutions of collagen becomes less as the irradiation time is increased. 3. The principal effect of ultraviolet irradiation is the fission of the primary collagen peptide chains, eventually yielding chain lengths incapable of stabilizing a helical structure. 4. Irradiation in both air and nitrogen results in a loss of tyrosine, histidine and phenylalanine, with more denaturation occurring in the presence of nitrogen.
| S-EPMC1264903 | biostudies-other
Project description:To cope with the shortage of filtering facepiece respirators (FFRs) during the coronavirus (COVID-19) pandemic, healthcare institutions were forced to reuse FFRs after applying different decontamination methods including gamma-irradiation (GIR). The aim of this study was to evaluate the effect of GIR on the filtration efficiency (FE) of FFRs and on SARS-CoV-2 detection. The FE of 2 FFRs types (KN95 and N95-3 M masks) was assessed at different particle sizes (0.3-5 µm) following GIR (0-15 kGy) delivered at either typical (1.65 kGy/h) or low (0.5088 kGy/h) dose rates. The detection of two SARS-CoV-2 RNA genes (E and RdRp4) following GIR (0-50 kGy) was carried out using RT-qPCR assay. Both masks showed an overall significant (P < 0.001) reduction in FE with increased GIR doses. No significant differences were observed between GIR dose rates on FE. The GIR exhibited significant increases (P ≤ 0.001) in the cycle threshold values (ΔCt) of both genes, with no detection following high doses. In conclusion, complete degradation of SARS-CoV-2 RNA can be achieved by high GIR (≥ 30 kGy), suggesting its potential use in FFRs decontamination. However, GIR exhibited adverse effects on FE in dose- and particle size-dependent manners, rendering its use to decontaminate FFRs debatable.
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Project description:Developing strategies for the radiosensitization of cancer cells by the inhibition of genes, which harbor low toxicity to normal cells, will be useful for improving cancer radiotherapy. Here, we focused on a β-site of amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1; β-secretase, memapsin-2). By functional inhibition of this peptidase by siRNA, it has also recently been shown that the DNA strand break marker, γH2AX foci, increased, suggesting its involvement in DNA damage response. To investigate this possibility, we knocked down BACE1 with siRNA in cancer cell lines, and sensitization to γ-irradiation was examined by a colony formation assay, γH2AX foci and level analysis, and flow cytometry. BACE1 knockdown resulted in the sensitization of HeLa, MDA-MB-231, U2OS, and SAOS cells to γ-irradiation in a diverse range. BACE1 knockdown showed a weak radiosensitization effect in osteosarcoma U2OS cells, which has a normal p53 function. HeLa and SAOS cells, which harbor p53 dysfunction, exhibited a greater level of radiosensitization. These results suggest that BACE1 may be a potential target for the radiosensitization in particular cancer cells.
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Project description:Radiotherapy is a frequently used treatment for oral cancer. Extensive research has been conducted to detect the mechanical properties of dental hard tissues after irradiation at the macroscale. However, little is known about the influence of irradiation on the tribological properties of enamel at the micro- or nanoscale. Therefore, this study aimed to investigate the effect of gamma irradiation on the wear behaviour of human tooth enamel in relation to prism orientation. Nanoscratch tests, surface profilometer and scanning electron microscope (SEM) analysis were used to evaluate the friction behaviour of enamel slabs before and after treatment with identical irradiation procedures. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were performed to analyse the changes in crystallography and chemical composition induced by irradiation. Surface microhardness (SMH) alteration was also evaluated. The results showed that irradiation resulted in different scratch morphologies, friction coefficients and remnant depth and width at different loads. An inferior nanoscratch resistance was observed independent of prism orientation. Moreover, the variation of wear behaviours was closely related to changes in the crystallography, chemical composition and SMH of the enamel. Together, these measures indicated that irradiation had a direct deleterious effect on the wear behaviour of human tooth enamel.
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Project description:Contamination of animal and poultry feeds by Fusarium and the mycotoxin Fumonisin B1 is frequent in the feed supply chain. The present study evaluated the prevalence of fumonisin B1 producing Fusarium among irradiated and non-irradiated animal and poultry feed mixtures. Further, the efficiency of γ-rays (2.5, 5.0, 7.5, and 10.0 kGy) to minimize Fusarium growth and biosynthesis of fumonisin B1 in artificially inoculated feed was evaluated. A total of 108 feed samples were collected in which 45.37% of feed mixtures were contaminated with Fusarium species. Among the contaminated samples, the frequency levels of F. verticillioides and F. proliferatum were 42.59 and 24.07%, respectively. Out of the 98 Fusarium isolates from feed samples, 84.7% of F. verticillioides and 64.28% of F. proliferatum were positive for FUM1 set of primers. Fumonisin B1 biosynthesis by the FUM1 positive isolates in feed was confirmed by LC/MS which recorded 0.1-45 µg/g of feed. Fungal growth and viable count of Fusarium in PDA medium and feed decreased with increasing irradiation dosage. Interestingly, fumonisin content was 11 µg/g of feed in 2.5 kGy irradiated sample as compared to 5 µg/g of feed in non-irradiated control. Ionizing radiation at 7.5 kGy was found lethal for fungal growth and fumonisin production. Our findings suggest that γ-radiation above 7.5 kGy effectively prevented fungal growth in feed mixtures and minimized the exposure of animal and human life to the potential risk of mycotoxin. Also it is necessary to maintain proper storage system for feeds until consumption.
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Project description:Demineralized dentin matrix (DDM) treated with gamma irradiation (GR) has shown promising results as an allograft without any adverse effects in in vivo and clinical studies. The purpose of this study was to evaluate the effects of 15 and 25 kGy GR on the osteoinductive properties of DDM at extra-skeletal sites. As a control group, non-irradiated DDM powder was implanted into the right subcutaneous tissues of the dorsal thigh muscles of 20 nude mice. DDM powder irradiated with 15 and 25 kGy was implanted into the left side. After two and four weeks, the bone mineral density (BMD) was measured with dual-energy X-ray absorptiometry. After confirming osteoblast- and osteoclast-specific activities by alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP) staining, a histological analysis was performed to measure the new bone formation and the number of osteoblasts and osteoclast-like cells on the surface of the DDMs. Histomorphometry was used to calculate the new bone formation area on the surface of the DDM particles (DDMs). The BMD in all the groups increased from two and four weeks without statistically significant differences. The osteoblasts were dominantly activated on DDM without GR, and DDM treated with 25 kGy compared to DDM treated with 15 kGy. Among the groups, new bone formation was identified in all the groups at each time point. In conclusion, GR at doses of 15 and 25 kGy does not affect the osteoinductive properties of DDM powder.
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